In drilling oil and gas wells, it is desirable to obtain information concerning potentially productive earth formations penetrated by the well as each such zone is drilled through. For example, it is desirable to obtain a sample of fluids produced from each formation to determine whether it is oil, gas or water. It is also desirable to measure the flow rate of the fluids and the temperature and pressure in the zone. Numerous systems and methods have been used for these purposes.
Early systems required that the drill string be removed from the borehole. Then a test system would be lowered back into the borehole, possibly on the end of the drill string from which the drill bit had been removed. Such drill stem test systems usually included a packer for isolating the zone to allow pressure testing. They usually included pressure and temperature sensors and recorders and chambers for collected fluid samples. While these are able to collect good information, they are expensive to operate because of the need to remove and replace the drill string twice in order to test and then return to drilling.
To reduce costs, various systems have been developed for performing formation testing through a drill string without pulling the drill string and without removing the drill bit. However, these systems tend to be complicated and therefore expensive and prone to failure. Systems for inflating and deflating packers to provide the necessary formation isolation have been complicated, often including down hole pumps and fluid reservoirs. Such systems typically occupy space in the normal mud flow path through the drill string and interfere with running test equipment through the mud flow path to the bottom hole location.
Therefore, there is a need for simple and robust systems suitable for use in a drill string for inflating and deflating formation isolating packers and for opening and closing flow paths for formation testing and for reverse circulation.